The present invention relates to an exhaust system for a marine gas turbine which may enhance the performance of an exhaust diffuser.
In general, it is possible to enhance the efficiency by enlarging the exhaust chamber of a gas turbine and also elongating the diffuser disposed in the exhaust chamber. However, since an exhaust chamber assembly of a marine gas turbine has to be incorporated into an engine space of a ship, in some cases, it is impossible to enlarge the exhaust chamber assembly. In such cases, the diffuser performance must be sacrificed in order to shorten its length, and an optimum shape thereof is sought therefor.
FIG. 3 is a schematic view showing a conventional exhaust system for a marine gas turbine. This type of exhaust system is most frequently designed and used, and called a "Long diffuser" type. In this exhaust system for a conventional marine gas turbine, an end portion of an exhaust diffuser 2, having a circular cross-section and arranged substantially horizontally, is inserted into a central portion of an exhaust chamber 1. An outlet of the end of the exhaust diffuser 2 is cut vertically. A boss 3 having a circular cross-section and provided with heat-insulating and sound-absorbing material is assembled coaxially in the interior of the exhaust diffuser 2.
The exhaust gas of the marine gas turbine flows in the interior of the doughnut-shaped and substantially horizontally arranged exhaust diffuser 2 while decreasing its velocity. The exhaust gas is diffused in the exhaust chamber 1 and is introduced into an exhaust eductor 4 connected to an upper portion of the exhaust chamber as indicated by an arrow.
In the case in which the space where the conventional exhaust system of the marine gas turbine is installed is limited, the exhaust chamber becomes small in size, and the length of the exhaust diffuser becomes short. Accordingly, a pressure restoring coefficient (which is represented by a pressure loss coefficient Cp; the higher the value, the greater the diffuser performance) which represents the performance of the exhaust diffuser is low. The efficiency becomes worse.